Organic sulfide catalyzed condensation reactions



United States Patent Ofiice 2,698,340 Patented Dec. 28, 1954 ORGANIC SULFIDE CATALYZED CONDENSA- TION REACTIONS Joseph K. Mertzweiller, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 20, 1951, Serial No. 222,140

17 Claims. (CL 260-475) This invention relates to improved methods of conducting organic condensation synthesis reactions. More particularly, this invention relates to an improved method of preparing organic esters, acetals, and unsaturated ethers having a total carbon number of 6 to 40 carbon atoms by condensation reactions, utilizing a sulfur-containing catalyst selected from the group consisting of alkyl mercaptans and alkyldithioalkanes.

This application is a continuation in part of U. S. application No. 61,913 filed November 24, 1948, since issued as U. S. Patent No. 2,578,724 dated December 18, 1951.

Organic synthesis condensation reactions, i. e., those involving the condensation of two or more molecules of organic compounds with the evolution of water, such as esterification, synthesis of acetals, unsaturated ethers, etc., are generally catalyzed by the addition of mineral acids or strong organic acids such as trichloroacetic or toluene sulfonic. While these are generally effective catalysts, they may, in certain cases, be subject to certain disadvantages such as producing excessive discoloration of the products and polymerization.

In addition, these catalysts result in the formation of sulfur bodies in the product, which, because of their high boiling point, cannot readily be removed from the products.

It has now been found that particular sulfur-containing catalysts, i. e., those selected from the group consisting of alkyl mercaptans and alkyldithioalkanes, are ideally adapted to overcome the beforementioned difficulties. The indicated reactions can be conducted in the manners generally known in the art, except for the utilization of the catalysts of this invention as taught.

The catalysts of this invention are stable under normal reaction conditions and do not react with a system, as contrasted to the use of toluene sulfonic acid. For example, use of toluene sulfonic acid as catalyst in esterification reactions leads to production of high-boiling sulfonates with resultant contamination of the products with sulfur.

The particular catalysts of this invention can also be chosen of a boiling point such that they boil at a lower point than the desired product. They can thus be readily removed, leaving a sulfur, catalyst-free product, as contrasted with other catalysts of the art.

Those alkyl mercaptans and alkyldithioalkanes having a total carbon number in the range of 6 to 16 are preferable. Particularly eflective and desirable compounds of the class of compounds of this invention are lauryl mercaptan, n-heptyl mercaptan, iso-octyl mercaptan, and n-amyl disulfide. The catalysts are utilized in the reaction system in a range of 0.01 to 0.10 weight per cent based on the component not present in excess (e. g., on

aldehyde in ether synthesis or on acid in certain esterifications). parable to toluene sulfonic acid, and are possessed of none of the beforementional difiiculties of the latter. The reagents function as solvents, but auxiliary solvents may be employed if desired.

As stated above, the reactions are conducted in conventional manner, except for the modification of the indicated catalysts used in the indicated manner.

Esters, and particularly the phthalic acid esters, can thus be prepared from alcohols of the desired carbon number by any of the otherwise conventional methods, as by reacting the alcohol with the acid, or with acid anhydride, or by first transforming the alcohol into an In this small quantity they have activities com-' alkyl halide and then reacting the latter with a metal salt of the selected acid. For example, phthalate esters may be prepared efliciently by reacting about 2 mols of a suitable alcohol with 1 mol of phthalic anhydride in the presence of the catalysts of this invention and using a solvent such as benzene as entrainer.

The catalytic esterification reaction is carried out at a pot temperature of about 100-200 (3., depending upon the boiling point and amount of entrainer. It can thus be seen that the esterification reaction is carried out in the conventional manner except for the incorporation of the indicated catalysts in the reaction mixture. The isooctyl phthalate ester itself boils at about ZOO-220 C., at 2 mm. of mercury pressure. The reaction is carried out in corrosion resistant equipment such as glass-lined equipment.

The process to yield the acetals and unsaturated ethers is also quite simple and economical in operation. The alcohol and aldehyde, which can have either the same or different carbon skeleton structures and are preferably of the more desirable branched chain carbon structures, are heated together under heating conditions such as might be employed for an esterification. Temperatures of from 80 C. to 235 C. are conveniently employed. Entrainers permit of lower temperatures and the higher temperatures are employed in the absence of auxiliary entrainers. Mixtures of aldehydes and alcohols such as might be obtained from synthetic methods are conveniently employed. The temperature must be adjusted properly such that the unsaturated ether may be formed at a sufiiciently great reaction rate as to make the operation of a practical nature. Unreacted starting materials, catalyst and certain lower boiling by-products including water can be removed from the system by distillation, since normally the unsaturated ether will be the highest boiling material present in any substantial amount. This affords a'convenient method for isolation of the product. Unreacted aldehyde and alcohol along with catalyst can be removed by volatilization from the reaction mixture and can, of course, be subjected to the reaction again to increase conversion to the unsaturated ether. The most practical procedure is to carry out at least the latter part of the distillation under reduced pressure to reduce product decomposition and tar formation. The quantity of water which is produced during the initial stages of the reaction period prior to distillation-of the product can be used as a convenient indication of the extent of completion of the reaction. If it is desired to remove the unsaturated ether product from the reaction mixture by distillation, this should be done at reduced pressures to avoid decomposition.

The molar ratios of the reactants are not critical and various mixtures of aldehydes and alcohols may be conveniently employed. Any reasonable excess of either aldehyde or alcohol is readily recycled. A moderate excess of alcohol appears to favor the reaction. For instance, the aldehyde to alcohol mol ratio may be advantageously held at about 1:3.

Since water is a by-product, the reaction is facilitated by removal of Water and gives increased unsaturated ether formation. This water removal may be conveniently handled by addition of an entrainer such as-benzene,

toluene, or the xylenes. The water is thus removed as one component of an azeotrope, the components of the azeotrope are separated, and the entrainer subsequently recycled. .Catalyst may be recycled with unconverted components. This makes advantageous the employment of a catalyst which boils Within the range of unconverted components.

The aldehydes and alcohols which may be converted to the unsaturated ethers and acetals by this improved technique include any of those of the aliphatic series. For best yields of the acetals and unsaturated ether, it has been discovered that the more highly branched aldehydes and alcohols are much to be preferred.

The reactants employed need not be chemically pure components but can be operated with mixtures. The process is especially useful for use on synthetic mixtures such as can be produced by reacting various higher olefins with carbon monoxide and hydrogen, a reaction commonly known as the 0x0 reaction. Aldehydes and alcohols from other types of synthetic-sources may also be used. The. present process. offers a very advantageousv method for converting crude distilled fractions which contain both 4 quired to attain 100% conversion. employed. in. this work.

No entrainer was higher alcohols and aldehydes such as those having six to Catalyst None mHePWl Mercaptan ten. carbonatoms. to highly useitaul. ended relatively efasily 5 isolatable product. This use 0 cru mixtures 0 rev v wants infact, n f olttstanding adyanlages; of rii ia iiigfii filliiii zffilif ifiiiil T 212 538 this; novel process. The. process; is also. one. ofi greatslm- 'lj m 380-410. 380410 380-410 plicity, both in the operational. procedure. and in the ap- 312 paratus necessary. 7 I 10 The unsaturatedethers. and acetals axe ildentlfied. 1111 the This example illustrates the efiicacy of the catalysts. of usual way b.y determlnatiom of the. bromine. nwnber, mohi in ntion, l fi w e e -a ly Infra fl yS The advantages of the catalysts of this invention can show. thecharacterls le ol finic and 88 i -l i be seen to. include. activities equivalent to. that of toluene bani T y q y yl flndstare. substantlally 14) sulfonic acid, no coloration of-prodhcts, and the facilitaabsent... Comparison. of the. elemental analysls. wit]: the tion of the obtaining of'a pure product. calculatedvaluesgtves. an additionalcheckon the stnuc- The acetals produced have utility in other synthesis tureof thecompounds formed. I reactions such as in the preparation of resins and chemical Th1s1ttvent1on1s lllustrated by. thefiollowmg examples; additives. The: esters. are well known.- as among. the best 9 5 plasticizersfor various resins. Theunsa-turatedethersate Example g ifgzi-g ig marinated 81 useful. as modifiers. in polymerization; reactions. and: as

v r v fuel oiladditivcs. Mixtures of the specified Cs; alcohol, Cs. aldehyde and It will, be: understood further. that the fOIBgQlHg excataly t t-. refluxed 1H 1 8 fili-Pafalllse i i g Of ampleshavebeen'given merely for. purposes-0t illustration, a. boiling. fiasl'e. of appropnate. s1ze,. water trap. and con.- but that other modifications of the present invention. are denser- Entramers such. as. benzene or: toluene. were empossible without departing from thescope of the. apployed in some. instances). The. water. 1L"I1.l.( 181l01. was pended. claims. measured. as a function of time and conversions. of al- What. is: claimed is:. dehyde calculated. on thlsbasis- I The. reaction rates. were 1'. In; a processfor the preparation: of an organic comtaken as 10 times. the. reciprocal of the time required; to pound of 6 to carbon atoms per molecule selected from attain conversionofi'aldehyde. Typical results. are the group. consisting; of acetals, unsaturated ethers and as. follows esters by a reaction wherein an. alcohol is condensed with I Lauryl' nrHeptyI Tso-Octyl' n-Amyl Toluene Sul- Cam-l t .N0ne. :Merca. Me ca M .13 1.

" t mead tan t an ill? s53 Catalyst: (1011a,, Wt. Percent, l

onAld 0. 01a 0.0710" 0. 091" 0.066 0. 005 0,10 AIcohoL. i Aldehyde; (l): Mel Ratio; Ale/Ali". 1.84. 1.75, 1.38. 1.5. 1. 5 1.5 11.5 Entrainer; I p (i);

.em F-; 225 21? 200- 213 212: 212 225 Time, Min. tor-50% Conmbf f Qua w 4 as. as. I s0. s4 38 72 Benelux 0 0.12 1 0:33. 1 0:27 0. 29.- 0.20, 0.14-

it-ethyl hexanol. I 2 ethyl-hexaldehydm. 'Benzenm. 4 (No-reaction).- It is apparent that equivalent results'were obtained with a member. of thegroup consisting of aldehydes, organic the catalysts of this invent-1on i'n conversion rates as comcarboxyli'c acids and organic carbox-ylic anhydridcs and pared with the action of toluene sulfonic acid. 5 wherein water is split: out, the improvement which com- 5 prises employing a sulfur-containing catalyst selected from Example ggg iii-i gi gggz gz the group consisting of. alkyl Inercaptans and alkyl dithi'oalkanes', both having 6' to 16 carbon atoms per mol- Similar reactions were conducted; as in Example 1; execule; cept that in this example no entramers. were employed. 2. A process according to claim 1 wherein the catalyst The-results follow': boils in the range of the unconverted reactants.

n-ne ty1. isooetyl :n-am 1 Ilso col; 1. Catalyst Mcrcagtan Mercaptandisulfiiie disulfige Catalyst 0011., Wt. Per- 1 cent OD'Al'dGhYdB O. 006 0; 01 0. 0088 0. (I16 0. 032. 0:12

('0 (X (l p 2; 2.8 2. 3. 2. 2.9 Temp *1 350450 350-450 350450 350450 350-450 350 450 1311110,. Mint. for 50% Aldx. 1

(101137,; A. 120. 32 I 46 20.. s4 33:

2.-ethyl hexane]. 2-ethyl hexaldehydm These results Show that. good. conversion rates were ob- 3-. In; a,- process for the preparation of an oxygenated tamed without the. use. of entramers. organic compound selected from. the group consisting ofacetals and unsaturated ethers by a condensation reaction Example Estenficatfm of a Ca alcoholanda Ca aldehyde,theimprovement which The esterification of phthalic anhydride with a Ca 211- 30 comprises employmg a sulfur-containing catalyst selected cohol, namely Z-ethyl hexanol was carried out in a similar manner,.the.conversionof phthalic anhydride being measured bywater elimination. Since: it is desirable toattain 1.00%, conversion. of phthalic. anhydride in this reaction,

from the group consisting of alkyl mercaptans and alkyl dithioalkanes, both having acarbon number inthe range of 6 to 16 carbon atoms.

4.. A process. according; to; claim. 3. wherein. the; catalyst the. catalytic. effect. measured in.- terms of the. time re. S5 boils imtherange of; the unconverted reactants.

5. The process of claim 3, including the additional step of taking overhead by distillation evolved water and the catalyst and thereafter isolating the oxygenated organic compound product.

6. In a process for the preparation of an ester utilizing a condensation reaction of an organic acid derivative selected from the group consisting of phthalic acid and phthalic anhydride with a C8 alcohol, the improvement which comprises employing a sulfur-containing catalyst selected from the group consisting of alkyl mercaptans and alkyl dithioalkanes, both having a carbon number in the range of 6 to 16 carbon atoms.

7. The process of claim 6, including the additional step of taking overhead by distillation evolved water and the catalyst and thereafter isolating the ester product.

8. A process as in claim 6, in which the catalyst is lauryl mercaptan.

9. A process as in claim 6, in which the catalyst is nheptyl mercaptan.

10. A process as in claim 6, in which the catalyst is isooctyl mercaptan.

11. The process of claim 6 in which the ester prepared is di-iso-octyl phthalate, the acid is phthalic acid and the alcohol is iso-octyl alcohol.

12. A process as in claim 3, in which the catalyst is lauryl mercaptan.

13. A process as in claim 3, in which the catalyst is n-heptyl mercaptan. v

14. A process as in claim 3, in which the catalyst is iso-octyl mercaptan.

15. A process as in claim 3, in which the catalyst is n-amyl disulfide.

16. A process for the preparation of di(Z-ethyl hexyl) phthalate which comprises reacting phthalic anhydride and 2-ethyl hexanol in the presence of n-heptyl mercaptan, taking overhead by distillation evolved water and the n-heptyl mercaptan and thereafter isolating the di(2-ethyl hexyl) phthalate product.

17. A process for the preparation of di(2-ethyl hexyl) phthalate which comprises reacting phthalic anhydride and 2-ethyl hexanol in the presence of iso-octyl mercaptan, taking overhead by distillation evolved water and the isooctyl mercaptan and thereafter isolating the di(Z-ethyl hexyl) phthalate product.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,907,822 James May 9, 1933 2,045,560 Fenske June 23, 1936 2,482,725 Bramwyche et a1 Sept. 30, 1949 

1. IN A PROCESS FOR THE PREPARATION OF AN ORGANIC COMPOUND OF 6 TO 40 CARBON ATOMS PER MOLECULE SELECTED FROM THE GROUP CONSISTING OF ACETALS, UNSATURATED ETHERS AND ESTERS BY A REACTION WHEREIN AN ALCOHOL IS CONDENSED WITH A MEMBER OF THE GROUP CONSISTING OF ALDEHYDES, ORGANIC CARBOXYLIC ACIDS, AND ORGANIC CARBOXYLIC ANHYDRIDES AND WHEREIN WATER IS SPLIT OUT, THE IMPROVEMENT WHICH COMPRISES EMPLOYING A SULFUR-CONTAINING CATALYST SELECTED FROM THE GROUP CONSISTING OF ALKYL MERCAPTANS AND ALKYL DITHIOALKANES, BOTH HAVING 6 TO 16 CARBON ATOMS PER MOLECULE. 